Piggy Back Convectors?

Neil_5

I have the recessed convectors, and I noticed on the element themselves, there is a cap plug on both ends (well one end have the bleeder).

Can I piggy back another element on these two ports to increse my output? Two units in parallel?

Also the inside of the cabinets are dark and do feel cold as they are recessed into outside walls, would placing insulation that is used to wrap ducts against the pack panel help?

Thanks,
Neil